The BBC's Rupert Wingfield-Hayes in Tokyo says Japan made an unwritten agreement with China in the 1970s that serving leaders would not visit the shrine.

Mr Abe appears to have broken that deal, our correspondent says.

In August, Mr Abe sent a ritual offering to the shrine but was not among a group of dozens of Japanese politicians who visited Yasukuni.

During an earlier period in office between 2006-2007 he said he would not even discuss visiting the shrine "as long as the issue remains a diplomatic problem".

Yasukuni commemorates some 2.5 million Japanese men, women and children who have died in wars.

But the souls of hundreds of convicted WW2 criminals are also enshrined there.

Fourteen so-called Class A criminals - those who were involved in planning the war - are among those honoured. They include war-time leader General Hideki Tojo, who was executed for war crimes in 1948.

Mr Abe's grandfather, Nobusuke Kishi, was minister of industry for much of the war. He was arrested after Japan's surrender but was never charged and went on to serve as prime minister.